The purpose of this invention is to establish overpressure protection for devices used to measure various quantities and qualities of fluid systems. Some of these quantities and qualities are pressure, temperature, humidity, flow, etc. This device allows for overpressure protection without the necessity for relieving the total quantity of fluid which can be delivered through the fluid carrying elements (i.e., pipeline) leading to the sensing device. This is desirable, since if protection is established by relieving the elements ' full fluid carrying capacity, the relieving device becomes large and expensive. The invention is intended for protecting cable pressurization monitoring devices such as pressure transducers, flow transducers, pressure contactors, etc. These devices are normally subjected to pressures below 15 psig but occasionally may be subjected to higher pressure during component testing. The invention can be used for other purposes.
The protection device consists of an inlet flow controlling port followed by a pressure relieving poppet, and lastly a larger delivery port which connects to the sensing device.
The inlet flow control port is sized significantly smaller than the poppet relieving port. The sizing is determined by the pressure, P.sub.1, the delivery duct might carry to the sensing device and the pressure, P.sub.2, the sensing device is cable of withstanding. The size relationship is such that the inlet port is restrictive enough to limit flow with pressure differential P.sub.1 - P.sub.2 to the flow the poppet relieving port can carry with pressure differential P.sub.2 -- atmospheric pressure or the normal discharge pressure of the environment at the exhaust of the relieving port.
In the case of protecting a cable pressure transducer (operating range of 0 - 10 psig and maximum pressure capability of 30 psig), an overpressure supply could be as high as 100 psig. This pressure could be carried through an inlet duct of 3/8 inch tubing. To protect the transducer from 30 psig overpressure would normally require a relieving device with a port size of 3/4 inch diameter. The selection of a proper ratio of inlet port diameter to poppet port effective diameter will allow for a maximum of 30 psig delivery through the delivery port. The actual size of the inlet port will be determined by the requirements of the sensing device. For example, if the sensing device requires large volumes of fluid, a very small inlet port will result in response time lags of the sensed quantity or quality. System requirements will dictate the necessary considerations as to response.
Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.